1. Field of the Invention
The present invention relates generally to the fabrication of magnetic heads for hard disk drives, and particularly to the fabrication of magnetic shields for the read head portions of such magnetic heads.
2. Description of the Prior Art
To increase the areal data storage density of hard disks for hard disk drives, the data tracks upon such hard disks are written closer together, such that a greater number of tracks per inch are recorded. To efficiently read data from a data track, the read head portion of a magnetic head of a hard disk drive must be shielded from extraneous magnetic fields, such as those generated by adjacent data tracks, commonly known as side reading effects, and magnetic shields are provided in magnetic head designs to provide such magnetic shielding for the read head active components.
Such prior art magnetic shields typically consist of a single thin film layer of ferromagnetic material, such as NiFe. However, because these prior art magnetic shields are single layer elements, magnetic edge effects, as are known to those skilled in the art, exist to cause the magnetic fields within the shields to separate into a plurality of magnetic domains. Such domains have magnetic fields of varying strengths and directions within the shield, such that domain boundaries are created between the magnetic domains in the shield layer. These domain boundaries and the magnetic fields within the various domains, move under the influence of external fields, such as are created from adjacent data tracks. These shifting magnetic fields within the shield itself are detectable by the sensitive active layers of the read head, and contribute to the background noise in the read head signal.
The present invention seeks to solve this problem by stabilizing the magnetic fields within the magnetic shields of the read heads, such that side reading is minimized, noise is reduced and the signal to noise ratio of the magnetic head is thereby increased.
The hard disk drive of the present invention includes a magnetic head wherein the magnetic shields of the read head portion of the magnetic head are magnetically stabilized. Each magnetic shield is preferably fabricated as a laminated structure including a plurality of ferromagnetic material layers that are separated by spacer layers composed of a nonmagnetic material. In the preferred embodiment, the spacer layer is preferably composed of ruthenium, and the magnetization of the adjacent ferromagnetic layers is oppositely directed, whereby the magnetization within the adjacent ferromagnetic layers becomes antiparallel coupled. Due to the coupling, the magnetic fields in the ferromagnetic layers establish single domain states having flux closed ends, and the laminated shield structure has stabilized magnetic field properties. A preferred embodiment of the present invention includes NiFe ferromagnetic layers, having an alternating thickness of approximately 600 xc3x85 and approximately 100 xc3x85, that are separated by a ruthenium spacer layer having a thickness of approximately 8 xc3x85. The laminated magnetic shields of the present invention may be utilized in merged magnetic heads as well as magnetic heads having separate read head and write head portions.
It is an advantage of the magnetic head of the present invention that it produces a read signal with reduced background noise.
It is another advantage of the magnetic head of the present invention that the magnetic shields of the read head are magnetically stabilized.
It is a further advantage of the magnetic head of the present invention that the magnetic shields of the read head have single domain magnetic fields.
It is an advantage of the hard disk drive of the present invention that it includes a magnetic head having a read head with reduced side reading problems, such that hard disks having an increased number of tracks per inch can be read effectively.
It is another advantage of the hard disk drive of the present invention that it includes a magnetic head of the present invention that it has a read signal with reduced noise.
It is a further advantage of the hard disk drive of the present invention that it includes a magnetic head of the present invention wherein the magnetic shields of the read head are magnetically stabilized.
It is yet another advantage of the hard disk drive of the present invention that it includes a magnetic head of the present invention wherein the magnetic shields of the read head have single domain magnetic fields.
These and other features and advantages of the present invention will no doubt become apparent to those skilled in the art after having read the following detailed description which makes reference to the several figures of the drawings.